Chapter One ends with an enigmatic statement from Chief Broom, who is the narrator. Broom seems to be not entirely in control of his mental faculties; he sees Nurse Ratched turn into a terrible robot, and believes that the hospital uses a machine to control the minds of the inmates. However, he claims that he will be truthful in the following narrative:

I been silent so long now it's gonna roar out of me like floodwaters and you think the guy telling this is ranting and raving my God; you think this is too horrible to have really happened, this is too awful to be the truth! But, please. It's still hard for me to have a clear mind thinking on it. But it's the truth even if it didn’t happen.
(Kesey, One Flew Over the Cuckoo's Nest, Google Books)

Broom's comment at first seems to indicate that he is going to make things up and lie about the story that follows, and that he is doing it deliberately. However, the line really reveals a stronger undercurrent of insanity in Broom's mind; he knows what the "truth" is regardless of the actual events, and he is ready to relate the events exactly as he experienced them. The events might not be factually correct, but they are his experiences, and that makes them the truth. It also indicates that not everything in the narrative is intended to reflect reality; if something is odd, it might exist solely in Broom's head. However, these events have all been subjectively experienced by Broom, making them as valid as the real "truth."